A sinusoidal oscillator is the stimulation source of a micro-impedance spectroscopy. The accuracy of its output frequency and waveform dictates the accuracy of the measured complex tissue impedance. In this study, an area-efficient low-power sinusoidal oscillator is developed for applications requiring low-power high-density bio-impedance measurements. Instead of using traditional LC tank based topology, the proposed sinusoidal oscillator implements a series of hyperbolic tangent functions to approximate the sine function. To achieve the continuous sinusoidal oscillation, a sine waveform shaper, a ramp signal generator, and a fully differential driver are developed for the proposed sinusoidal oscillator. To minimize the power dissipation, a low power supply voltage, 0.5 V, is used in the circuit. Designed in a standard 0.13-μm CMOS process, the proposed sinusoidal oscillator can generate continuous sinusoidal signal with a tuning range of 10 Hz–4 kHz. It dissipates power of < 3 μW and occupies an area of 0.07 mm2.
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